Humans aren’t the only species whose males place a big emphasis on having a large appendage. There are plenty of examples out there. Elk grow antlers, peacocks grow giant tails and rhinoceros beetles grow a ridiculous-looking contraption on the front of their forehead.

According to classic Darwinism, these traits are a way for the male to say, “Hey baby, look at me!” Though many such ornamentations are completely useless practically speaking, they seem to play some sort of role in the mating process. The question then becomes, however, why don’t the weaker individuals just mimic the large appendages to get some action?

It turns out, they don’t because they can’t.

It’s been a long-held belief that growing large horns or antlers is in some way tied to how “fit” the individual is as a mate. For example, if an animal is big and strong, they can more easily hunt down food and then can put more energy into growing antlers rather than keeping warm. Now, thanks to a new paper published last week in Science from Michigan State University, it turns out that this theory is correct. In fact, it’s even more correct than previously believed.

The study – conducted in part by Ian Dworkin, zoologist at Michigan State University – has shown that the growth of these ornaments are directly tied to the insulin levels of the animals in question. Thus, the more food an animal can get its paws on, the higher its insulin levels, and the bigger antlers, horns or feathers it grows.

The researchers lowered the insulin levels in otherwise healthy and active male rhinoceros beetles. As a result, their trademark long horns grew to much shorter lengths. What’s more, the finding has been discovered to also be true of other animals with similar display ornamentation.

The finding also ties a neat little bow around the reason why weaker animals don’t try to cheat by mimicking the flashy ornamentation.